Pax Britannica (Latin for "British Peace", modelled after Pax Romana) was the period of relative peace between the great powers during which the British Empire became the global hegemonic power and adopted the role of a "global policeman".
Between 1815 and 1914, a period referred to as Britain's "imperial century", around of territory and roughly 400 million people were added to the British Empire. Victory over Napoleonic France left the British without any serious international rival, other than perhaps Russia in Central Asia. When Russia tried expanding its influence in the Balkans, the British and French defeated them in the Crimean War (1853–1856), thereby protecting the Ottoman Empire.
Britain's Royal Navy controlled most of the key maritime trade routes and enjoyed unchallenged sea power. Alongside the formal control exerted over its own colonies, Britain's dominant position in world trade meant that it effectively controlled access to many regions, such as Asia, North America, Oceania, and Africa. The British also, much to the dismay of other colonial empires, helped the United States uphold the Monroe Doctrine which upheld its economic dominance in the Americas. British merchants, shippers and bankers had such an overwhelming advantage over those of other empires that in addition to its colonies it had an informal empire.
After losing the Thirteen Colonies, a significant part of British America, in the American Revolution, Britain turned towards Asia, the Pacific and later Africa with subsequent exploration leading to the rise of the Second British Empire (1783–1815). The Industrial Revolution began in Great Britain in the late 18th century and new ideas emerged about free markets, such as Adam Smith's The Wealth of Nations (1776). Free trade became a central principle that Britain practiced by the 1840s. It played a key role in Britain's economic growth and financial dominance.
From the end of the Napoleonic Wars in 1815 until World War I in 1914, the United Kingdom played the role of global hegemon (most powerful actor).